1. Field of the Invention
The present invention relates generally to manifolds of hot runners for metal molds used in the injection molding of synthetic resins, and a method of manufacturing such manifolds, and more particularly, to a manifold of hot runners for metal molds of injection molding machines, which is designed to be separated into an upper plate and a lower plate, and is provided with a ground channel pipe covered with a copper plate for keeping the temperature of a flow channel constant, thus forming the desired flow channel for the synthetic resins, and a method of manufacturing such a manifold.
2. Description of the Prior Art
Generally, manifolds of hot runners for metal molds used in the injection molding of synthetic resins have been manufactured by forming, using a gun drill, a flow channel in a steel plate having a single structure for bearing injection pressure, and then grinding the flow channel.
However, the conventional manifold has a problem that it is difficult to grind the interior of a flow channel hole bored by the gun drill. Furthermore, the conventional manifold has another problem that angled corners are formed at junctions where two or more holes bored by the gun drill meet when manufacturing a manifold of a complicated shape, since a boring process using the gun drill is carried out along a straight line.
That is, in FIGS. 4 and 5 showing a conventional manifold, the gun drill bores holes in a manifold 11 having a single structure such that the holes forming flow channels are intersected with each other. Therefore, the flow channels 12 formed in the manifold 11 meet at right angles, thus making angled corners 13. Such angled corners 13 may hinder smooth flow of synthetic resins. In order to solve the above problem, a special method may be used. However, such a special method unreasonably causes an increase in manufacturing costs of the manifolds.
When synthetic resins flow to the angled corners 13, the angled corners 13 cause a thermal decomposition of the synthetic resins or turbulence thereof, thus leading to a structural failure of glass fiber contained in the synthetic resins as a reinforcing additive.
In addition, since the conventional manifold is formed in a single structure, it is impossible to repair the manifold even when foreign materials are caught in the flow channel or the synthetic resins in the manifold lose fluidity due to carbonization. Therefore, the hot runner is not preferably used in the injection molding of synthetic resins sensitive to heat.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a separable manifold of hot runners for metal molds of injection molding machines, which is manufactured by designing the manifold in such a way as to be separated into an upper plate and a lower plate, forming a groove on the lower plate for receiving ground channel pipes therein, inserting the ground channel pipes into the groove, covering the channel pipes with copper plates, and assembling the upper plate with the lower plate.
Another object of the present invention is to provide a method of manufacturing the separable manifold of hot runners for the metal molds of injection molding machines, comprising the steps of: designing the manifold in such a way as to be separated into an upper plate and a lower plate, manufacturing joint blocks to be set on the junctions of two or more flow channels formed on the lower plate; forming a groove on the lower plate for receiving channel pipes therein; installing the joint blocks at the junctions where two or more channels meet; covering the channel pipe inserted into the groove with copper plates; connecting the channel pipe covered with the copper plates to the joint blocks; and assembling the upper plate with the lower plate.